Gulf of Maine Warming Update: 2022 the Regions Second Warmest Year

Documenting one more year in a decade of above-average regional temperatures

Author

Adam Kemberling

Published

February 1, 2023

Annual Sea Surface Temperatures

With an annual average sea surface temperature (SST) of 53.66°F — more than 3.72°F above normal — the Gulf of Maine experienced its 2nd warmest year on record in 2022. This year fell short of the previous warmest year on record — 2021 — 0.43°F, but was record-breaking in a number of regards.

In nine of the twelve months this year, average monthly SST was within the top 3 warmest among all years. The most extreme temperatures this year occurred in November and December, each setting new record highs. Monthly temperatures ranked lowest during July and September (ranked 8th and 6th respectively), but were still within the top ten for each of those months. These temperatures all contribute to what has been a decade-long pattern of above-average temperatures in the area.

Worldwide Temperatures

It was not just the Gulf of Maine that experienced exceptional warmth in 2022, however. Globally, 2022 was the 3rd warmest year for sea surface temperatures, and 6th-warmest year for combined land & ocean temperatures..

Figure 6 shows annual average SST anomalies for oceans all over the world in 2022. While much of the Southern Ocean and expanses of the southeastern Pacific were anomalously cool (a feature of La Niña conditions), most of the world’s oceans experienced unusually warm temperatures in 2022. This is particularly true for northern mid-latitudes, especially the northwestern Pacific (off Japan) and along the eastern seaboard of the United States—a region that includes the Gulf of Maine.

Figure 6: Map of annual average sea surface temperature anomalies for the world’s oceans in 2022.

Daily Sea Surface Temperatures

The annual cycle of SST in the Gulf of Maine exhibits a familiar pattern with the lowest temperatures observed in March, with the highest SSTs observed in August (Figure 7). The average difference between the annual maximum SST in August and the annual minimum SST in March is 22.87 °F. In 2022, the difference between the maximum SST (Aug-07, 68.72°F) and minimum SST (Mar-19, 42.15°F) was 26.57 °F. Daily SST anomaly values in 2022 never fell below +1.59 °F and reached as high as +7.36 °F above the long-term average. The largest temperature anomalies were observed on November 7th, when they breached 7 °F above the long-term average.

A line chart shows the average sea surface temperature for each day of the year, and overlaid against it are notably smoother black lines representing the long-term mean, 10th percentile, and 90th percentile temperatures for those same days of the year. The area between the mean and the observed temperature is filled in with a solid color to indicate whether that day meets marine heatwave criteris. The observed temperatures for 2022 are above the 90th percentile for nearly the entire year, with the exception of two periods less than a week long in June and October.

Figure 7: A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from January 1 through December 301 2022. Black lines representing the long-term (i.e., 1982 – 2011) average SST, the 10th percentile (i.e., cold spell threshold), and 90th percentile (i.e., heatwave threshold) for a given day in the Gulf of Maine are labeled to indicate climatological reference points. A solid line (red for marine heatwave or blue for a non-heatwave day) indicate the observed SST for each day; red and blue shading illustrates whether each day is considered part of a MHW event.

Record Setting Daily Temperatures

Daily SST values in 2022 were some of the highest ever recorded in the Gulf of Maine. Record daily high SSTs were set for more than half of all days in November and December, with new records set in all months but July (?@fig-percent-record-bars). The most daily records for a single month occurred in November, which experienced record high SSTs for 24 of the month’s 30 days - or 80% of the month. In total, record high daily temperatures were reached on 169 days in 2022; nearly 46% of the year experiencing record high SSTs.

Figure 8: An illustration of the percentage of days during each month in 2022 when a record-high temperature was observed in the Gulf of Maine (e.g., 80% — 24 days — of November were new record-setting high temperatures).

More Persistent, Intense Heatwaves

A marine heatwave (MHW) is defined as a period when there are five or more consecutive days when the observed SST is greater than the 90th percentile of the long-term average for that day. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event.

Figure 7 shows the long-term average SST (line labeled “Climatological Mean”), as well as the threshold for being a MHW day (line labeled “Heatwave Threshold”) or a marine cold spell MCS day (line labeled “Cold Spell Threshold”). The colored line and shaded area in the figure shows the observed SST for that day and its distance from the climatological average; when it is red, the Gulf of Maine is experiencing MHW conditions. The Gulf of Maine met the criteria for MHW status for 353 days in 2022.

Comparing daily SST anomalies and MHW status for 2022 to the long-term record (Figure 9), as in the figure below — it becomes clear that the frequency, duration, and intensity of MHWs has not only increased in the past decade. In a world without human-caused climate change, we would expect, positive (warm) and negative (cool) SST anomalies to more or less balance out over the span of several years, as various patterns of natural climate variability alternate having a dominant influence in Earth’s climate (e.g., La Niña vs El Niño). What is being observed in the Gulf of Maine (and elsewhere around the world), however, is a loss of that balance: larger fractions of recent years are experiencing above average temperatures and cold spells are becoming vanishingly rare.

A figure displays the temperatures for each day of year as a colored stripe, organized with a row for each day such that the day of year aligns vertically. The lower two-thirds has a roughly equal balance between colors for warm (red) and cold (blue) temperature anomalies. The top third of the image is almost completely red as temperature anomalies rarely fall below the long-term average. Black dots are overlaid onto days that meet the criteria for a heatwave, they are rare in the lower section and common in the red section.

Figure 9: Heat map of daily SST anomalies from the beginning of 1982 through the end of 2022. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Warming Rate

GMRI research was the first to reveal that the Gulf of Maine has been warming faster than the vast majority of the world’s ocean. Figure 10 updates this historical analysis by including data for 2022. Indeed, the story has not changed: the Gulf of Maine is warming faster than ~96.6% of the world’s ocean. The reason why this is so important is because the rate of change can have profound consequences for the biology of individual species and for the integrated ecology of entire food webs. Marine species are responding to warming trends by adjusting their latitudinal range and the depths that they occupy in attempts to track their preferred conditions. Not all species are capable of tracking rapid environmental change, and scientists are concerned that ecosystem resilience will decline as the environment outpaces the communities they once supported.

Figure 10: Maps illustrating the rate of warming (from 1982 through 2022) displayed as their relative percentiles for [left] the northwest Atlantic Ocean and [right] entire global ocean surface.

Concluding Thoughts:

In recent years, SSTs in the Gulf of Maine (and adjacent waters) have increased significantly and the rate of warming has accelerated. Combined, these climate-related impacts are beginning to have profound consequences for the marine ecology in the Gulf of Maine, with implications for the people and communities who rely on marine resources for their livelihoods and well-being. Research suggests there are two major factors driving these trends, one oceanographic and one atmospheric:

  1. Oceanographic: The Gulf of Maine is influenced by two primary oceanic currents: the Labrador Current and the Gulf Stream. Historically, there was a stronger influence of the Labrador Current on the water in the Gulf of Maine. That stronger flow helped keep the heat transported northward along the U.S. East Coast by the Gulf Stream further out to sea. More recently, scientists have observed changes occurring in the interplay between the Labrador Current and Gulf Stream. More Arctic-origin freshwater from melting sea ice and land-based ice is constricting the southward flow of the Labrador Current. This is allowing the Gulf Stream—which transports warm water from lower latitudes to spread out more at latitudes around the Gulf of Maine. This, in turn, allows warmer water, more heavily influenced by the Gulf Stream to “spill over” into the Gulf of Maine.

  2. Atmospheric: The North Atlantic Oscillation (NAO)— a large-scale pattern of natural variability in the atmosphere — has been in a “positive phase” more frequently over the past 10-15 years, meaning a more zonal (i.e., west-to-east) atmospheric pattern has dominated in the region. The relative decrease in “waviness” of the jet stream inhibits more consistent intrusions of cooler, Arctic air into the region.

While the oceanographic driver of the observed SST change in the Gulf of Maine has clear links to human-caused climate change, more research is needed to ascertain whether the NAO is experiencing significant changes as a result of anthropogenic climate change. Regardless, the atmospheric and oceanic conditions of the past several years combine to reveal an unambiguous trend: The Gulf of Maine is experiencing unprecedented warmth—and is heating up at a rate that is faster than almost anywhere else in the world’s oceans.


A Note on Data Sources

  • NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.

Recommended Citation:

Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2022. https://gmri.org/stories/warming-22

Marine Heatwave Technical Report Preview:

The study of Marine heatwaves is a relatively new area of study. Scientists here at GMRI were first to use the phrase when they brought public attention to the extreme temperatures in the Gulf of Maine during 2012. The concept of a “marine heatwave” emerged as a way to communicate a rare phenomenon where temperatures were much higher than the observed historical and seasonal fluctuations. These extreme conditions caught scientists’ attention for their ecological & economic consequences, and they became a tool for studying future climate-change-related impacts before they occur elsewhere.

As temperatures increase globally, SST observations that were once rare have become more and more common. Understanding this pattern, scientists now are considering new ways to define what it means to be a marine heatwave. Debate has now emerged on how “best” to identify and measure the impacts of these rare events. GMRI scientists are part of this evolving discussion among the international community that is weighing the trade offs in these proposed changes.

In an upcoming technical report series, GMRI scientists will be covering this discussion in detail. Explaining the rationale between the competing approaches, how scientists think about their impacts, and how the heatwave record for the Gulf of Maine can change with these decisions.


OLD ASSETS:

Temperature Anomaly Horizons

One way to think about the severity of these changes is to think about temperature horizons. A temperature horizon captures how long temperatures remain above certain thresholds. Each threshold is designated its own temperature, and in this way we can see how long within a year temperatures remained: 1 to 2 or as much as 4\(^oC\) above normal.

Horizon plot of all years and their temperature anomaly horizons

Figure 11: Temperature anomaly horizons for all years of available satellite data (1982-2022). Horizons display how long temperatures were above certain thresholds (horizon width) and are colored by the strength of these events.

Comparing the Gulf’s Two Hottest Years

If we pull the horizons of our two hottest years on record it makes it easier to contrast where either one experienced acute high temperature events, and where there were sustained periods of above average temperatures.

Early into 2022 it was apparent that the year was on-par with the previous title-holder for warmest year on record.

Single year horizon plots comparing 2021 and 2022

Figure 12: Two horizon plots compare the timing and duration of elevated temperatures in the two warmest years on record, 2021 and now 2022. The width of a color horizon indicates the duration that temperatures were above that threshold.

The Balance of Hot and Cold

Another way to visualize the climate transition that we are observing is by looking at the fraction of each year spent in different temperature ranges. Under a steady climate we would expect over the long-term to spend similar amounts of the year experiencing relatively warm & cold temperatures. These periods would balance themselves out and we would on-average have experienced something similar to the long-term climate.

What we have been seeing in the Gulf of Maine recently has lost that sense of balance. Larger fractions of the year are shared by above average temperatures & cold spell events are becoming vanishingly rare.

Streamplot tracking fraction of each year spent in varying degrees of temperature anomalies

Figure 13: A streamplot shows the fraction of each year on record that temperature anomalies fell within ranges further from the climate reference period average. Since 2010 the Gulf of Maine’s temperatures shifted rapidly outside of this expected range and a large fraction of the year is now 2 degrees or more above that average (red).

 

A work by Adam A. Kemberling

Akemberling@gmri.org